1. Field of the Invention
This invention relates generally to a method and analyzer for detecting and measuring the amount of water (moisture) in a fluid. More particularly, this invention relates to a method and analyzer for detecting and measuring water in chemical process fluid streams over a wide range of water concentrations.
2. Background
Many chemical reactions leading to the production of organic products such as isocyanates, polyethers, and others, should be conducted in the absence of water to prevent loss of yields, products contamination, and the possible damage to equipment due to the formation of solids. Additionally, in many cases where acidic materials such as hydrogen chloride, phosgene and chlorine are used or formed in a chemical process, introduction of water from external sources such as a heat exchanger or humid air must be excluded as water could react or ionize such species to form extremely corrosive conditions which could be detrimental to plant equipment and operation.
In order to assess if the presence of water in a process stream has reached a serious proportion and corrective action should be taken, it is desirable that a suitable analyzer be available for detecting the presence of water and providing a indication of the concentration thereof. However, to be effective with various chemical processes, the analyzer must be capable of measuring a wide range of concentrations, from a few parts-per-million (ppm) to percentage levels.
Known commercial analyzers available at the present time are not capable as a unit to perform a wide range of water analysis. Conventional spectroscopic analyzers, such as near-infrared detectors, are neither suitable for the measurement of very low moisture concentrations (0-50 ppm), nor for concentrations higher than 1000 ppm of water. Such analyzers are not capable of detecting the low concentrations of water, and at the higher concentrations, the water tends to produce emulsions with organic systems such as benzene, chlorobenzene, toluene and the like, which are opaque to light, and render it impossible to make measurements. Electrochemical water analyzers, such as coulometric, amperometric, and dielectric constant analyzers, are suitable for low water concentration measurements (0-1000 ppm), but are not suitable for analysis when the concentration is above 1000 ppm due to lack of measurement linearity.